This invention relates generally to a poured flowable flooring particularly applicable for sub-floors commonly installed in multifloored structures, such as apartment buildings, industrial complexes, office buildings and also for those buildings which are rehabilitated while retaining the existing structure.
The most relevant prior art is believed to be best represented by U.S. Pat Nos. 4,075,374 and 4,159,912. In the '374 patent, a mix of calcium sulfate hemihydrate with a latex emulsion composition, water and sand was found not suitable in actual use. The deficiencies of the '374 patent are set forth in the '912 patent. The mix of the '912 patent is apparently in widespread use. Although the '912 patent overcame the deficiencies of the '374 patent, it has been found in some instances that when the aforementioned mixes set up, the topmost surface has a dusty or dust-like surface. Where the mix is poured as a sub-flooring, the uppermost surface in these floors in some instances must be treated, such as by cleaning and sealing in order to successfully apply the final top flooring.
The present invention relates to cementitious products of certain physical characteristics which are particularly adapted for sub-floors. The sub-floors are typically of the type wherein there is an existing substrate onto which a slurry-like mix is poured. Typically, the mix comprises calcium sulfate hemihydrate, water, sand and other additives. The additives enhance particulate distribution, drying time, crystalline formation, strength and surface characteristics.
Broadly, my invention comprises a composition of calcium sulfate hemihydrate with additives to prevent foaming, to extend the set up time, enhance mixing and, most importantly, to control crystalline structure and prevent or inhibit `dusting` on the top finished surface. The additive which provides these last-mentioned properties is a vinyl polymer. With my invention, the composition is mixed with sand and water, and the sand is uniformally suspended in the mix for a long period of time, say for up to two hours, during which time the mix sets up.
Typically, when such mixes `set up`, excess water migrates to the top surface and carries with it fine particulates. As the evaporation continues to completion, these particulates settle out and deposit on the topmost surface which results in a powdery residual of particulate material. This is, the particulates migrate to the top surface which is easily chipped or damaged and may require further treatment prior to application of the actual floor.
My composition allows the mix to set to final hardness without the formation of a top dusty surface and requires less water than most commercially available comparable mixes. A particular polymeric material is added to the composition which polymeric material is believed to prevent the migration of the particulate material to the top surface during the evaporation step. Although the exact chemical phenomenon involved is not fully understood, what is known is that a product is provided which sets with a dust free, crack resistant surface under normal conditions of use prior to the application of finish flooring.